U.S. patent number 10,658,833 [Application Number 15/669,114] was granted by the patent office on 2020-05-19 for conductor temperature detector.
This patent grant is currently assigned to Solaredge Technologies Ltd.. The grantee listed for this patent is Solaredge Technologies Ltd.. Invention is credited to Meir Adest, Yoav Galin, Israel Gershman, Guy Sella.
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United States Patent |
10,658,833 |
Galin , et al. |
May 19, 2020 |
Conductor temperature detector
Abstract
Various implementations described herein are directed to a
method for detecting, by a device, an increase in temperature at
certain parts of an electrical system, and taking appropriate
responsive action. The method may include measuring temperatures at
certain locations within the system and estimating temperatures at
other locations based on the measurements. Some embodiments
disclosed herein include an integrated cable combining electrical
conduction and heat-detection capabilities, or an integrated cable
or connector combining electrical conduction with a thermal
fuse.
Inventors: |
Galin; Yoav (Raanana,
IL), Adest; Meir (Raanana, IL), Gershman;
Israel (Yehud, IL), Sella; Guy (Bitan Aharon,
IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
Solaredge Technologies Ltd. |
Herzeliya |
N/A |
IL |
|
|
Assignee: |
Solaredge Technologies Ltd.
(Herzeliya, IL)
|
Family
ID: |
60573156 |
Appl.
No.: |
15/669,114 |
Filed: |
August 4, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170358920 A1 |
Dec 14, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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15078450 |
Mar 23, 2016 |
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62376693 |
Aug 18, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02S
40/36 (20141201); H01H 33/02 (20130101); H02H
1/0015 (20130101); G01K 11/06 (20130101); H02J
7/35 (20130101); H02S 40/34 (20141201); H02H
3/334 (20130101); H01H 85/04 (20130101); H02J
3/38 (20130101); H02J 3/385 (20130101); H02J
3/381 (20130101); H02J 2300/26 (20200101); G08B
17/06 (20130101); Y02E 10/56 (20130101); Y02E
10/58 (20130101) |
Current International
Class: |
H02H
3/00 (20060101); H02S 40/34 (20140101); G01K
11/06 (20060101); H02J 7/35 (20060101); H02S
40/36 (20140101); H02J 3/38 (20060101); H01H
33/02 (20060101); H01H 85/04 (20060101); H02H
1/00 (20060101); H02H 3/33 (20060101); G08B
17/06 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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101609971 |
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Sep 2012 |
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CN |
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102272936 |
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Apr 2014 |
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CN |
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103888058 |
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Jun 2014 |
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CN |
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103888061 |
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Jun 2014 |
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CN |
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104471415 |
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Mar 2015 |
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CN |
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202006007613 |
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Aug 2006 |
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DE |
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2827077 |
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Jan 2003 |
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FR |
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10-1550588 |
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Sep 2015 |
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KR |
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87/02835 |
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May 1987 |
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WO |
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99/67862 |
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Dec 1999 |
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WO |
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2014027043 |
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Feb 2014 |
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WO |
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Other References
Jan. 2009--Chou--Automatic Diagnosis System of Electrical Equipment
Using Infrared Thermography, 2009, pp. 1-13. cited by applicant
.
Feb. 1, 2018--EP Search Report, EP App. No. 17186631.2. cited by
applicant .
Mar. 3, 2020--CN Office Action--CN 201710129079.1. cited by
applicant.
|
Primary Examiner: Jackson; Stephen W
Attorney, Agent or Firm: Banner & Witcoff, Ltd.
Parent Case Text
RELATED APPLICATIONS
The present application also claims priority to U.S. Provisional
Patent Application Ser. No. 62/376,693, entitled "Conductor
Temperature Detector," filed Aug. 18, 2016, which is hereby
incorporated by reference in its entirety. The present application
is a continuation-in-part (CIP) application of U.S. patent
application Ser. No. 15/078,450, entitled "Conductor Temperature
Detector," filed Mar. 23, 2016, which is hereby incorporated by
reference in its entirety.
Claims
What is claimed is:
1. An apparatus comprising: a first conductor and a second
conductor, the first conductor and the second conductor being in
electrical contact; a spring disposed between the first conductor
and a first surface, wherein the spring is loaded to apply a force
to the first conductor; and a pellet disposed between the first
conductor and a second surface, the pellet sized and positioned to
prevent unloading of the spring and designed to deform at a
predetermined temperature, wherein, upon the pellet deforming at
the predetermined temperature, the spring is configured to unload
in a direction toward the first conductor so as to break the
electrical contact between the first conductor and the second
conductor, and wherein one conductor of the first conductor and the
second conductor is connected to an electrical input for receiving
photovoltaic power, and the other conductor of the first conductor
and the second conductor is connected to an electrical output for
providing photovoltaic power.
2. The apparatus of claim 1, wherein the pellet is designed to
deform at a temperature of about 200 degrees Celsius.
3. The apparatus of claim 1, further comprising a photovoltaic
generator, wherein the first conductor, second conductor, spring
and pellet are disposed in a connector terminal of the photovoltaic
generator.
4. The apparatus of claim 1, further comprising a photovoltaic
power device, wherein the first conductor, second conductor, spring
and pellet are disposed in an output connector of the photovoltaic
power device.
5. The apparatus of claim 4, wherein the connector of the
photovoltaic power device is a male output connector terminal for
connecting to a female output connector of a second photovoltaic
power device.
6. The apparatus of claim 4, wherein the connector of the
photovoltaic power device is a female output connector terminal for
connecting to a male output connector of a second photovoltaic
power device.
7. The apparatus of claim 4, wherein the photovoltaic power device
comprises at least one of a direct current to direct current
converter and a direct current to alternating current
converter.
8. The apparatus of claim 4, wherein the photovoltaic power device
is integrated in a photovoltaic generator junction box.
9. An apparatus comprising: a first photovoltaic module comprising
a first electronic circuit and a first circuit terminal; a
connector coupled to the first circuit terminal and configured to
connect to a terminal or a connector of a second electronic
circuit; and a thermal fuse disposed in or next to the connector,
the thermal fuse designed to disconnect the first electronic
circuit from the second electronic circuit in response to an
increase in temperature in or next to the connector.
10. The apparatus of claim 9, wherein the photovoltaic module
comprises a photovoltaic generator.
11. The apparatus of claim 9, wherein the photovoltaic module
comprises a battery.
12. The apparatus of claim 9, wherein the photovoltaic module
comprises a combiner box.
13. The apparatus of claim 9, wherein the photovoltaic module
comprises at least one of: a direct current to direct current
converter and a direct current to alternating current
converter.
14. The apparatus of claim 9, wherein the thermal fuse is designed
to disconnect the first electronic circuit from the second
electronic circuit in response to a temperature of about 200
degrees Celsius.
15. A photovoltaic string comprising: a plurality of photovoltaic
generators, each photovoltaic generator having a plurality of
output connectors; wherein each photovoltaic generator has a first
output connector electrically connected to a second output
connector of a different photovoltaic generator, forming a
connection point; and wherein at least one of the first and second
output connectors comprise an integrated thermal fuse designed to
disconnect the first output connector from the second output
connector at a predetermined temperature.
16. The photovoltaic string of claim 15, wherein the integrated
thermal fuse is designed to disconnect the first output connector
from the second output connector at a temperature of about 200
degrees Celsius.
17. The photovoltaic string of claim 15, wherein each of the
photovoltaic generators comprises a junction box, each junction box
comprising at least one of a direct current to direct current
converter and a direct current to alternating current
converter.
18. The photovoltaic string of claim 17, wherein each of the
photovoltaic generator junction boxes further comprises a
temperature sensing device responsive to an increase in temperature
in or next to one or more of the output connectors and a controller
configured to receive measurements from the temperature sensing
device and trigger an overheating response in response to a
measurement indicating overheating.
19. The photovoltaic string of claim 18, wherein the overheating
response comprises raising an alarm.
20. The photovoltaic string of claim 18, wherein the overheating
response comprises reducing current flowing through the output
connectors.
Description
BACKGROUND
Faulty connectors and/or conductors may cause overheating of
components in electrical systems, and in some cases may even cause
fires. Arc detection circuits might not always be triggered in
cases of overheating. Overheating of conductors may be an
especially acute problem in renewable power systems (e.g.
photovoltaic and wind-power systems), where temperatures of system
components may already be high due to exposure to the sun and the
heating of components during power generation and conversion.
Additionally, connectors may be prone to overheating due to the
erosion of electrical contact mechanisms over time. Cost-effective
detection of overheating of sections of power systems which are not
adjacent to components containing logical circuitry (e.g.
connectors or conductor areas which are not adjacent to system
sensors and/or devices) may be an especially challenging task.
There is a need for effective solutions for rapid detection of and
response to overheating of components in such systems.
SUMMARY
The following summary is a short summary of some of the inventive
concepts for illustrative purposes only, and is not intended to
limit or constrain the inventions and examples in the detailed
description. One skilled in the art will recognize other novel
combinations and features from the detailed description.
Embodiments herein may employ temperature sensing devices
configured to detect overheating of components within a power
system.
In illustrative electrical systems, a temperature sensor may be
deployed a certain distance from a point considered susceptible to
overheating, such as a connection point. Since heat may dissipate
rapidly when traveling through a physical medium, the system may be
designed for placement of sensors close enough to susceptible
points to measure an increase in temperature which may trigger
preventative actions such as disconnecting elements of the
electrical system. In some systems, it might not be convenient or
cost-effective to place temperature sensors close enough to
sensitive points to detect overheating. In those systems, it may be
desirable to combine thermocouple (TC) or linear heat detection
(LHD) cables with the standard system conductors to allow detection
of excessive heat at longer distances.
In many electrical systems, especially those exposed to weather
conditions, connection points may be the most susceptible to
intrusion of moisture and dirt, which may lead to increased
electrical impedance and possible overheating. In some photovoltaic
electrical systems, faulty connectors have overheated, leading to
destructive fires. Therefore, many illustrative embodiments include
detecting overheating at or near connection points (e.g. placement
of a temperature sensor in or within 20 cm of a connection point),
though this disclosure is not limiting in that respect and applies
to overheating detection at other locations as well.
In some illustrative embodiments, designing for connector locations
near temperature sensors may help detect high temperatures. For
example, in certain systems such as some photovoltaic (PV)
installations, a connection point may be formed by connecting two
cables, with the connection point in proximity to a circuit (e.g. a
direct current to alternating current (DC-AC) inverter such as a
DC-AC micro-inverter, or a direct current to direct current (DC-DC)
converter). In cases where the cables are of significant length, by
designing cables of asymmetric length, proximity of each connection
point to a power device may be achieved. For example, each power
device may feature one cable 0.8 meters long, and one cable 0.2
meters long. In this case, if multiple power devices are coupled to
one another, each connection point is only 0.2 meters away from a
power device, and at that relatively short distance, a temperature
sensor adjacent to the power device may detect overheating at the
connection point.
In some embodiments, it may be desirable to detect overheating of
electrical conductors at locations which might not be near
connector locations. For example, in some photovoltaic
installations, portions of electrical conductors may be in contact
with metallic objects (e.g. outdoor metallic mounting structures
which reach high temperatures), and/or may be adjacent to an
inflammable agent (e.g. a wooden rooftop), and/or may be chewed on
and damaged by animals, increasing the risk of overheating.
Illustrative embodiments include integrated electrical cables
combining electrical conductors with heat detection devices (e.g.
thermocouple and LHD devices) which may detect overheating at
locations not adjacent to thermal sensors deployed by connection
locations.
Configuration of overheating detection systems and devices may vary
according to system characteristics and requirements. For example,
in some embodiments, a temperature threshold may be set to trigger
a response to prevent melting of electrical conductor insulation.
In some embodiments, a different temperature threshold may be set
to trigger a response to prevent a wooden rooftop from catching
fire or a tar roof coating from melting.
In some embodiments, a temperature threshold may be set at a
temperature sensor to prevent overheating to a certain temperature
at a location susceptible to overheating. The relationship between
the temperature measured by a temperature sensor at a sensor
location and the temperature at a location susceptible to
overheating may be different depending on the distances between the
two locations, the physical medium and the materials comprising the
components of the electrical system.
Responses to a potentially unsafe overheating condition may vary.
In some embodiments, a potentially unsafe overheating condition may
trigger an automatic action, such as opening safety switches to
disconnect the point of overheating from other circuitry. In some
embodiments, a potentially unsafe overheating condition may trigger
a disconnection of one or more thermal fuses disposed at electrical
connection points. In some embodiments, a potentially unsafe
overheating condition may trigger an overheating response such as
operating a power device (e.g., a power converter) to reduce power
drawn from a power source (e.g., a photovoltaic generator) and/or
reducing voltage or current provided at the output of the power
converter. In some embodiments, a potentially unsafe overheating
condition may trigger an overheating response such as triggering an
alarm system and/or updating a user interface monitored by a system
owner and/or system maintenance personnel.
In some systems, analyses of previous instances of overheating may
assist in predicting overheating events. For example, a system may
feature certain patterns of voltage and current levels in different
parts of the system prior to or at the early stages of overheating.
Since many systems include data logging of operating parameters
(e.g. voltage, current, frequency, harmonic content, solar
irradiance etc.), in some instances it is possible to predict
overheating based on measurements other than temperature, and take
preventative action.
As noted above, this summary is merely a summary of some of the
features described herein. It is not exhaustive, and it is not to
be a limitation on the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, aspects, and advantages of the present
disclosure will become better understood with regard to the
following description, claims, and drawings. The present disclosure
is illustrated by way of example, and not limited by, the
accompanying figures.
FIG. 1 is a flow diagram of a method for detecting overheating in
an electrical conductor according to one or more illustrative
aspects of the disclosure.
FIG. 2 is part-schematic, part block diagram of a system for
detecting overheating in an electrical conductor according to one
or more illustrative aspects of the disclosure.
FIG. 3 is part-schematic, part block diagram of a system for
detecting overheating in an electrical conductor according to one
or more illustrative aspects of the disclosure.
FIG. 4 is part-schematic, part block diagram of a system for
detecting overheating in an electrical conductor according to one
or more illustrative aspects of the disclosure.
FIG. 5 illustrates a portion of a photovoltaic string according to
one or more illustrative aspects of the disclosure.
FIG. 6 illustrates a photovoltaic panel according to one or more
illustrative aspects of the disclosure.
FIG. 7 illustrated a portion of a photovoltaic string according to
one or more illustrative aspects of the disclosure.
FIG. 8A depicts an integrated heat-detecting electrical conductor
according to one or more illustrative aspects of the
disclosure.
FIG. 8B depicts integrated heat-detecting electrical connectors
according to one or more illustrative aspects of the
disclosure.
FIG. 9 is a flow diagram of a method for detecting overheating in
an electrical conductor according to one or more illustrative
aspects of the disclosure.
FIG. 10 is a flow diagram of a method for predicting a potentially
unsafe condition according to one or more illustrative aspects of
the disclosure.
FIG. 11 is a block diagram of an illustrative distributed system
for carrying out some of the illustrative methods according to
aspects of the disclosure.
FIG. 12 depicts an integrated heat-detecting electrical connector
according to one or more illustrative aspects of the
disclosure.
FIG. 13A depicts a portion of a photovoltaic string according to
one or more illustrative aspects of the disclosure.
FIG. 13B depicts a portion of a photovoltaic string according to
one or more illustrative aspects of the disclosure.
FIG. 13C depicts a portion of a photovoltaic string according to
one or more illustrative aspects of the disclosure.
FIG. 14 depicts an integrated heat-detecting electrical connector
according to one or more illustrative aspects of the
disclosure.
FIG. 15 depicts a method for operating a power converter according
to one or more illustrative aspects of the disclosure.
DETAILED DESCRIPTION
In the following description of various illustrative embodiments,
reference is made to the accompanying drawings, which form a part
hereof, and in which is shown, by way of illustration, various
embodiments in which aspects of the disclosure may be practiced. It
is to be understood that other embodiments may be utilized and
structural and functional modifications may be made, without
departing from the scope of the present disclosure.
Reference is now made to FIG. 1, which shows a flow diagram of a
method for detecting overheating in an electrical conductor
according to one or more illustrative aspects of the disclosure. At
step 100, a temperature sensor may be deployed at a distance of
x[cm] from a point considered to be susceptible to overheating
(e.g. a connection point, hereafter referred to as "CP"). By
solving appropriate thermal differential equations, the temperature
at the CP may be estimated as a function of the temperature
measured by the sensor. In some embodiments, the relationship
between the temperature at the CP and the temperature measured by
the sensor may be empirically determined prior to deploying the
sensor and connecting conductors at the connection point. For
example, a sensor may be placed adjacent to a conductor in lab
conditions, with a connection point x[cm] away. The connection
point may be heated to a set of different temperatures, with the
various CP temperatures and corresponding sensor measurements
logged for future reference. In some embodiments, a lookup table
may be created, the lookup table relating the temperature at the CP
to the temperature measured by the sensor. The lookup table may be
saved to memory on a device carrying out the method of FIG. 1 for
reference during the course of the method, and/or may be used to
configure the device before carrying out the method of FIG. 1. In
some embodiments, CP temperatures and corresponding sensor
measurements may be used to create a mathematical model relating an
approximation of CP temperatures to the sensor measurements. The
mathematical model may be a linear, higher-order polynomial,
logarithmic, exponential or rational function. For example, in some
embodiments where the physical structure between the temperature
sensor and the CP comprises a single material and/or simple
geometric shapes, a linear approximation may suffice to obtain a
reasonably accurate approximation of the CP temperature. In some
embodiments where the physical structure between the temperature
sensor and the CP comprises multiple materials and/or sophisticated
geometric shapes, a higher-order polynomial, a logarithmic or
exponential function may provide a more accurate approximation of
the CP temperature.
The temperature sensor deployed at step 100 may be coupled to a
communication and/or processing device for receiving measurements
from the sensor and transmitting and/or processing the
measurements. For example, the sensor may output measurements onto
an information bus, and the measurements may be read by a control
device (e.g. a microprocessor, Digital Signal Processor (DSP),
Field Programmable Gate Array (FPGA), Application Specific
Integrated Circuit (ASIC) or other device), a communication device
(e.g. a wireless transceiver, a power-line-communication (PLC)
device and/or an acoustic communication device) and/or a memory
device. A control device may be coupled to the sensor within a
single device, or a control device may be remote and may process
measurements transmitted by a communication device.
At step 101, a control device may be configured to respond to a
temperature measurement above a threshold. The threshold may be
determined in accordance with solving equations relating the
temperature at the CP to the temperature measured at the sensor, or
in accordance to a relationship determined to exist between the
temperature at the CP and the temperature measured by the sensor
and stored by a lookup table as disclosed above. In some
embodiments, the threshold may be an absolute temperature. For
example, a threshold may be set to 100.degree. C., 200.degree. C.
or 300.degree. C. A fixed threshold may be set with regard to the
flammability of materials near the CP. For example, conductors used
in photovoltaic installations may be insulated using cross-linked
polyethylene (XLPE), polyvinyl chloride (PVC) or chlorinated
polyvinyl chloride (CPVC). XLPE-insulated conductors may have a
rated maximum conductor temperature of 90.degree. C., an emergency
rating of up to 140.degree. C. and a short-circuit rating of
250.degree. C. If protecting the insulation is desired, a threshold
may be set with regard to the emergency rating. Cables having PVC
or CPVC insulation or other types of insulation may feature
different ratings, and different thresholds may be set
accordingly.
In some embodiments, a threshold may be set with regard to the
flammability of structures supporting the electrical system. For
example, many photovoltaic electrical systems are mounted on
buildings having wooden roofs. The temperature at which wood begins
to burn depends on the type of wood, but typically, the pyrolysis
of wood begins at temperatures around 250.degree. C. Some roofs may
be coated with tar, which may begin to auto-ignite at about
315.degree. C. In some embodiments, a system may be configured to
not protect the conductor insulation from melting, but a response
to protect the supporting roof from catching fire may be
desirable.
In some embodiments, the threshold may be adaptive and may be set
with relation to a previously measured temperature or previously
measured system parameter values (e.g. voltage, current, solar
irradiance). For example, a threshold may be set as THRESH[.degree.
C.]=baseline[.degree. C.]+delta[.degree. C.], where
baseline[.degree. C.] may be a temperature measured over period of
time, and delta may be an increase in temperature over a period of
time. For example, if a sensor measures a steady temperature
100.+-.5[.degree. C.] for one hour, delta may be set to equal 50
[.degree. C.] and the threshold may be 100[.degree. C.]+50[.degree.
C.]=150[.degree. C.]. If the steady temperature decreases to
90.+-.5[.degree. C.] for one hour, delta may still be set to equal
50 [.degree. C.] and the new threshold may be 90[.degree.
C.]+50[.degree. C.]=140[.degree. C.]. In some embodiments, delta
may depend on baseline. For example, delta may equal 50[.degree.
C.] if baseline=100[.degree. C.], while delta may equal 45[.degree.
C.] if baseline=90 [.degree. C.]. In some embodiments, the
threshold may be set with regard to a probabilistic function. For
example, the method may be interested in the temperature at a
connection point, and the threshold may be set such that the
temperature at the connection point remains below a certain
temperature with high probability. For example,
empirically-obtained data and/or mathematical models may indicate
that when a sensor measures 100[.degree. C.], the temperature at a
connection point 20 cm away is above 90 [.degree. C.] with
probability 50%, and when the sensor measures 110 [.degree. C.],
the temperature at a connection point 20 cm away is above 90
[.degree. C.] with probability 80%. The threshold may be selected
to trigger a response with regard to the acceptable temperature at
the connection point and the probability of the acceptable
temperature being surpassed.
In some embodiments, different thresholds may be set depending on
other external variables. For example, temperature measurements may
be considered in conjunction with other sensor measurements, such
as voltage, current, solar irradiance, moisture or other
measurements. For example, in a system a first threshold may be set
to trigger a response if a temperature of 200.degree. C. is
measured 10 [cm] from an electrical connection and a current of 10
[A] is measured to be flowing through the connection, with a second
threshold set to trigger a response if a temperature of 180.degree.
C. is measured 10 [cm] from an electrical connection and a current
of 12 [A] is measured to be flowing through the connection.
In some embodiments, a system may be configured to respond to a
temperature remaining above one or more thresholds for a period of
time. For example, a system may be configured to respond to a first
threshold temperature of 200.degree. C. persisting for 10 seconds,
and to respond to a second threshold temperature of 160.degree. C.
persisting for 12 seconds.
In some embodiments, a threshold may be set with regard to an
increase in temperature. For example, a system may be configured to
respond to an increase of 10.degree. C. or more in 20 seconds or
less, regardless of the absolute temperatures measured. In some
embodiments, a system may be configured to respond to a variable
increase of temperature which varies depending on the absolute
temperature measured, as described above.
The thresholds described herein are only illustrative examples
which may be used in different systems. Various combinations
thereof may be applied to various electrical systems depending on
system characteristics and requirements. At step 102, the
temperature sensor may begin to periodically measure temperatures
for transmission to control and/or memory devices. At step 103, a
control device may compare a measured temperature to the threshold
obtained at step 101. If the temperature is below the threshold,
the operating conditions may be assumed to be safe and normal
system operation may continue, with the method returning to step
102. In some embodiments, the method may periodically return to
step 101, to recalculate the threshold based on current temperature
measurements. If, at step 103, a temperature equal to or greater
than the threshold is measured, the method may proceed to step 103,
where an overheating response such as a "high temperature protocol"
(HTP) is activated. In some embodiments, the HTP may comprise a
controller automatically disconnecting the connection point from
electrical current. In some embodiments, the HTP may comprise a
controller reducing the electrical current flowing through the
connection point, for example, by reducing power drawn from a power
source connected at the input to the power device. In some
embodiments, the controller may be coupled via a communication
device to a wired and/or wireless network(s)/Internet/Intranet,
and/or any number of end user device(s) such as a computer, smart
phone, tablet and/or other devices such as servers which may be
located at a network operations center and/or monitoring center.
These devices may be utilized to generate a warning of a dangerous
condition, determine when a dangerous condition is probable, detect
the type of dangerous condition and/or take action to degrade or
turn off certain portions a system. These warnings can be audio
and/or visual. They may, for example, be a beep, tone, siren, LED,
and/or high lumen LED.
Reference is now made to FIG. 2, which shows part of a system for
detecting overheating in an electrical conductor according to one
or more illustrative aspects of the disclosure. Power device 200
may be configured to receive input electrical power from a power
source (e.g. PV generator, wind turbine, hydro-turbine, battery,
supercapacitor, fuel cell, etc.) and output electrical power to a
load, such as an electrical device, a grid, a home, or a battery.
PV generators may include one or more solar panels, solar cells,
solar shingles, and/or strings (e.g. serial strings or parallel
strings) of solar panels or solar cells. Power device 200 may
comprise input conductors 203 for receiving electrical power, and
output conductors 204 for outputting electrical power. Power device
200 may comprise circuitry 202 for power processing, control,
monitoring, safety, and communication. Various elements comprising
circuitry 202 will be described in greater detail later on in this
disclosure. Circuitry 202 may receive power from input conductors
203, and output power via output conductors 204.
Still referring to FIG. 2, enclosure 207 may physically house the
electrical components comprising a photovoltaic module, for
example, power device 200. Enclosure 207 may be a closed or
partially closed compartment. In some embodiments, enclosure 207
may comprise a portion of a junction box for a photovoltaic module
(e.g. a PV generator), or may comprise a lid configured to fit to a
junction box for a photovoltaic module. Input conductors 203 may be
physically connected to enclosure 207 using an appropriate
connecting method, such as, in this illustrative embodiment, screws
206. In some embodiments, input conductors may be secured to the
enclosure by soldering, clamping or other methods. An electrical
connection between input conductors 203 and circuitry 202 may be
provided by a conducting path deployed between screws 206 and
circuitry 202. Similarly, output conductors 204 may be physically
connected to enclosure 207 using an appropriate connecting method,
such as, in this illustrative embodiment, screws 205. In some
embodiments, output conductors may be secured to the enclosure by
soldering, clamping or other methods. An electrical connection
between output conductors 204 and circuitry 202 may be provided by
a conducting path deployed between screws 205 and circuitry
202.
Still referring to FIG. 2, temperature sensor 201 may be deployed
adjacently to screws 205, and may be configured to transfer
temperature measurements to controller or communication device
(e.g. a controller or communication device included in circuitry
202). In case of overheating of one of output conductors 204, the
temperatures measured by temperature sensor 201 may increase.
Similarly, temperature sensor 210 may be similar to or the same as
temperature sensor 201 may be deployed near screws 206 and may
measure increases in temperature on or near input conductors 203.
Temperature sensors 201 and/or 210 may be thermocouple devices, IC
temperature sensors, silicon bandgap temperature sensors,
thermistors, or any other suitable temperature sensor.
Reference is now made to FIG. 3, which illustrates circuitry 302
such as circuitry which may be found in a power device such as
power device 200, according to an illustrative embodiment.
Circuitry 302 may be similar to or the same as circuitry 202
illustrated in FIG. 2. In some embodiments, circuitry 302 may
include power converter 300. Power converter 300 may comprise a
direct current-direct current (DC/DC) converter such as a buck,
boost, buck/boost, buck+boost, Cuk, Flyback and/or forward
converter. In some embodiments, power converter 300 may comprise a
direct current--alternating current (DC/AC) converter (also known
as an inverter), such a micro-inverter. In some embodiments,
circuitry 302 may include Maximum Power Point Tracking (MPPT)
circuit 306, configured to extract increased power from a power
source the power device is coupled to. In some embodiments, power
converter 300 may include MPPT functionality. MPPT functionality
may include, for example, a "perturb and observe" method and/or
impedance matching. Circuitry 302 may further comprise control
device 305 such as an analog control device, a microprocessor,
Digital Signal Processor (DSP), Application-Specific Integrated
Circuit (ASIC) and/or a Field Programmable Gate Array (FPGA).
Still referring to FIG. 3, control device 305 may control and/or
communicate with other elements of circuitry 302 over common bus
320. In some embodiments, circuitry 302 may include circuitry
and/or sensors/sensor interfaces 304 configured to measure
parameters directly or receive measured parameters from connected
sensors and/or sensor interfaces 304 configured to measure
parameters on or near the power source, such as the voltage and/or
current output by the power source and/or the power output by the
power source. In some embodiments, the power source may be a PV
generator, and a sensor or sensor interface may directly measure or
receive measurements of the irradiance received by the generator
and/or the temperature on or near the generator. In some
embodiments, sensor 301 may be part of sensors/sensor interfaces
304, and in some embodiments sensor 301 may be a separate sensor.
Sensor 301 may be similar to or the same as temperature sensor 201
of FIG. 2. For example, sensor 301 may be a temperature sensor
deployed near a connection to a conductor, to monitor the
temperature on or near the conductor to detect potential
overheating.
Still referring to FIG. 3, in some embodiments, circuitry 302 may
include communication device 303, configured to transmit and/or
receive data and/or commands from other devices. Communication
device 303 may communicate using Power Line Communication (PLC)
technology, acoustic communication technology, or wireless
technologies such as ZIGBEE.TM., Wi-Fi, BLUETOOTH.TM., cellular
communication or other wireless methods. In some embodiments,
circuitry 302 may include memory device 309, for logging
measurements taken by sensor(s)/sensor interfaces 304 and/or sensor
301, to store code, operational protocols or other operating
information. Memory device 309 may be flash, Electrically Erasable
Programmable Read-Only Memory (EEPROM), Random Access Memory (RAM),
Solid State Devices (SSD) or other types of appropriate memory
devices.
Still referring to FIG. 3, in some embodiments, circuitry 302 may
include safety devices 307 (e.g. fuses, circuit breakers and
Residual Current Detectors). Safety devices 307 may be passive or
active. For example, safety devices 307 may comprise one or more
passive fuses disposed within circuitry 302 and designed to melt
when a certain current flows through it, disconnecting part of
circuitry 302 to avoid damage. In some embodiments, safety devices
307 may comprise active disconnect switches, configured to receive
commands from a controller (e.g. control device 305, or an external
controller) to disconnect portions of circuitry 302, or configured
to disconnect portions of circuitry 302 in response to a
measurement measured by a sensor (e.g. a measurement measured by
sensor 301 or sensors/sensor interfaces 304). In some embodiments,
circuitry 302 may comprise auxiliary power unit 308, configured to
receive power from a power source coupled to circuitry 302, and
output power suitable for operating other circuitry components
(e.g. control device 305, communication device 303, etc.).
Communication, electrical coupling and/or data-sharing between the
various components of circuitry 302 may be carried out over common
bus 320.
Reference is now made to FIG. 4, which illustrates aspects of
illustrative embodiments. Power device 400 may comprise casing 407,
circuitry 402, input conductors 403, output conductors 404a and
404b and fastening screws 405 which may be similar to or the same
as similar components illustrated with regard to other embodiments
disclosed herein. For example, circuitry 402 may include some or
all of the components of circuitry 202 illustrated in FIG. 2.
Temperature sensor 401 may be similar to or the same as sensors 201
and 210 of FIG. 2. In the illustrative embodiment depicted in FIG.
4, no sensor is deployed adjacently to input conductors 403, but
alternative embodiments may include a sensor disposed adjacently to
input conductors 403 and/or additional sensors. Connectors 408a and
408b may be connected at the ends of output conductors 404a and
404b, respectively, and may be configured to connect to connectors
on other conductors fitted to be connectable to them. For example,
connector 408b may be a male connector, and connector 408a may be a
female connector. Connector 408b may be designed to be connected to
female connectors similar to connector 408a, and connector 408a may
be designed to be connected to male connectors similar to connector
408b.
In some electrical systems employing connectors similar to
connectors 408a and 408b, faulty connectors may lead to a faulty
electrical connection, which may cause arcing and/or overheating of
the connectors. Excess heat may spread for the connectors to the
conductors they are coupled to. In some systems, failure to detect
gradual overheating of connectors and/or conductors may cause
conductor insulation to catch fire, and significant damage and/or
dangerous situations may ensue.
Output conductors 404a and 404b may be of appropriate length for
connecting a plurality of power devices such as 400 when deployed
in an electrical installation. For example, power device 400 may be
designed to be a photovoltaic (PV) module or to be coupled to a
different PV module (e.g. a PV generator), and a plurality of power
devices similar to or the same as power device 400 may be coupled
in series or in parallel to form a photovoltaic string carrying the
power from a plurality of PV modules. In some embodiments, coupled
power devices such as 400 may be deployed a certain distance apart
from each other. For example, in some embodiments, adjacent power
devices may be deployed 1 meter or 2 meters apart from one another.
In some embodiments, each power device may comprise output
conductors of about equal length, where the sum of the lengths of
the conductors is about the same as the distance between the power
devices. For example, if two power devices (e.g. devices such as
power device 400) are deployed about 1 meter apart, each device may
comprise two output cables of about 0.5 meters each, so that the
male connector of one device's output conductors may be coupled to
the female connector of the other device's output conductors.
In some photovoltaic systems, detecting an increasing temperature
at connection points may be difficult due to significant distances
between system temperature sensors and connection point locations.
For example, common PV power devices include cables between around
50 [cm] and around 100 [cm] long. When two PV power devices are
coupled, the connector location may be between 50 [cm] and 100 [cm]
from a temperature sensor deployed in the PV power device, which
might be too great a distance for effective detection of
overheating at the connector location. In some embodiments,
enhanced overheating detection may be obtained by designed
connector locations to be close to a temperature sensor in the PV
power device.
In the illustrative embodiment of FIG. 4, output conductor 404a is
illustratively significantly shorter than output conductor 404b. As
a numerical example, output conductor 404a may be 0.2 meters long,
and output conductor 404b may be 0.8 meters long. When power
devices featuring asymmetrically sized output conductors are
coupled to each other, the connection point between the conductors
may be closer to one device than the other. As a numerical example,
if output conductor 404a is 0.2 meters long, and output conductor
404b is 0.8 meters long, when two power devices (e.g. devices such
as power device 400) are coupled to one another, the connection
location will be about 0.8 meters from one power device and 0.2
meters from the other power device. If one output conductor is very
short and the other is very long, the connection location may be
close enough to circuitry (e.g. temperature sensor 401) for the
circuitry to detect an increase in heat at the connection point. In
some embodiments, a thermocouple or LHD device may be deployed
alongside an electrical conductor and integrated in input or output
conductors (e.g. conductors 403, 404a and/or 404b) and coupled to a
controller and/or communication device deployed in circuitry 402 to
detect overheating at any point along the conductor.
Reference is now made to FIG. 5, which illustrates a portion of a
photovoltaic generation system according to aspects of illustrative
embodiments. PV panels 510a, 510b and 510c may be part of a serial
PV string. A PV panel may comprise a junction box (e.g. PV panel
510a comprises junction box 511a) designed to receive electrical
power from PV cells (not explicitly illustrated, as PV cells are
generally deployed on the opposite side of the panel as the
junction box). Conductors may carry power output from the junction
box. In some embodiments, power devices may be coupled to
photovoltaic panels for monitoring and/or controlling the power
output by the panels or for other operational or safety purposes.
For example, power devices 500a and 500b may be coupled to PV
panels 510a and 510b, respectively. Power devices (e.g. power
devices 500a, 500b and 500c) may be coupled in series, to form a
serial PV string. Conductor 520 may be coupled to the low-voltage
output conductor terminal of power device coupled to the first
panel in the string (in this illustrative embodiment, power device
500a coupled to PV panel 510a), and may form the lower-voltage
string line. A higher-voltage string line may be formed by serially
connecting the rest of the output conductors of the power devices
comprising the string. The lower-voltage and higher-voltage string
lines may be designed to be input to an appropriate device, for
example, a direct-current (DC) combiner box, battery charging
circuit or PV inverter designed to convert DC power produced by the
PV panels to alternating-current (AC) power for consumption by a
load (e.g. a home, grid or battery).
In the illustrative embodiment shown in FIG. 5, power device 500a
is coupled to PV panel 510a. Power device 500a receives power from
panel conductors 512a via input conductors 503a. Power device 500a
outputs power via output conductors 504aa and 504ba. Similarly,
power device 500b is coupled to PV panel 510b. Power device 500b
receives power from panel conductors 512b via input conductors
503b. Power device 500a outputs power via output conductors 504ab
and 504bb. Output conductors 504ba and 504ab are connected at
connection point CP, which may be adjacent to power device 500b. If
the connection between output conductors 504ba and 504ab at is
faulty, the temperature at connection point CP may increase, and
may be detected by a temperature sensor comprised by power device
500b (e.g. a sensor similar to or the same as sensors 201, 210 or
410 as described herein). Multiple power device may be coupled to
one another in a similar manner, enabling connecting points to be
adjacent to power devices configured to detect increases in
temperature.
In some embodiments, some or all of the power device input and/or
output conductors may include thermal devices designed to respond
to or measure rising temperatures. For example, in some
embodiments, some or all of the system conductors may include
thermocouple wires deployed alongside conductors designed to carry
the electrical power. In some embodiments, each system conductor
may include a thermocouple wire connected to a sensor in a power
device (e.g. power device 500a), enabling the power device to sense
a rise in temperature at any point along the conductor. In some
embodiments, costs may be reduced by deploying thermocouple wires
only in short conductors (e.g. input conductors 503a, 503b and
output conductors 504aa, 504ab). In some embodiments, each system
conductor may include a Linear Heat Detector (LHD) coupled to a
controller in a power device (e.g. power device 500a). In some
embodiments, a rise in temperature at any point along the conductor
may cause the LHD wires to come into contact with one another,
triggering an electrical pulse that may be detected by a controller
configured to take action in response to receiving a pulse. In some
embodiments, costs may be reduced by deploying LHD wires only in
short conductors (e.g. input conductors 503a, 503b and output
conductors 504aa, 504ab).
FIG. 5 illustrates a system comprising add-on power devices coupled
to PV panels. In some embodiments, some or all of the power device
functionalities may be embedded into a PV panel junction box.
Reference is now made to FIG. 6, which illustrates an integrated
photovoltaic panel according to illustrative embodiments. PV panel
610 comprises PV cells (not explicitly depicted) and junction box
607, configured to receive power from the PV cells. Junction box
607 may feature an integrated power device comprise some or all of
the functional elements described herein with regard to
illustrative power devices (e.g. some or all of the elements of
circuitry 302 described with regard to FIG. 3). For example,
junction box 607 may comprise a temperature sensor similar to or
the same as sensors 201 and 210, a controller similar to or the
same as control device 305, and a safety device such as switches
(e.g. Metal Oxide Silicon Field Effect Transistors (MOSFETs),
Insulated-Gate Bipolar Transistors (IGBTs), Bipolar Junction
Transistors (BJTs), electro-mechanical or solid-state relays, etc.)
configured to disconnect output conductors 604a and 604b. In some
embodiments, junction box 607 may include a power converter,
communication device and MPPT circuit which are similar to or the
same as power converter 300, communication device 303 and MPPT
circuit 306, respectively. Output conductors 604a and 604b may be
designed to carry the electrical power output from junction box
607, and may be fastened to connectors 608a and 608b, respectively.
Many common photovoltaic panels feature output conductors which are
about the same length, and may be of an appropriate length for
adjacent PV panels to be connected to each other. In some
embodiments of the current disclosure, such as in the embodiment
shown in FIG. 6, one conductor may be longer than the other. For
example, output conductor 604b may be significantly longer than
output conductor 604a. As a numerical example, output conductor
604b may be about 1.8 meters long, and output conductor 604a may be
about 0.2 meters long.
Connecting PV panels using asymmetrical conductors may, in some
embodiments, increase the likelihood of detecting a rise in
temperature due to a faulty connection. Reference is now made to
FIG. 7, which shows a portion of a PV string according to
illustrative embodiments. PV panels 710a, 710b and 710c may be
serially connected to form part of a PV string. A PV panel may
comprise a junction box (e.g. PV panel 710a comprises junction box
711a) designed to receive electrical power from PV cells (not
explicitly illustrated, as PV cells are generally deployed on the
opposite side of the panel as the junction box). Conductors may
carry power output from the junction box. Conductor 720 may be
coupled to the low-voltage output conductor of the first panel in
the string (in this illustrative embodiment, PV panel 710a), and
may form the lower-voltage string line. A higher-voltage string
line may be formed by serially connecting the rest of the output
conductors of the PV panels comprising the string. The
lower-voltage and higher-voltage string lines may be designed to be
input to an appropriate device a direct-current (DC) combiner box,
MPPT circuit, battery charging circuit or PV inverter designed to
convert DC power produced by the PV panels to alternating-current
(AC) power for consumption by a load (e.g. a home, grid or
battery).
In the illustrative embodiment shown in FIG. 7, PV panel 710a is
coupled to PV panel 710b. Conductor 720 may be coupled to the
lower-voltage conductor 704aa of panel 710a at connection point
CPa. PV panel 710a may be coupled to PV panel 710b by connecting
output conductor 704ba of panel 710a to output conductor 704ab of
panel 710b at connection point CPb. If the connection between
output conductors 704ba and 704ab at is faulty, the temperature at
connection point CPb may increase, and may be detected by a
temperature sensor disposed in junction box 711b (e.g. a sensor
similar to or the same as sensors 201, 210 or 410 as described
herein). Multiple PV panels may be coupled to one another in a
similar manner, enabling connecting points to be adjacent to PV
panels configured to detect increases in temperature.
In some embodiments, some or all of the PV panel output conductors
may include thermal devices designed to respond to or measure
rising temperatures. For example, in some embodiments, some or all
of the output conductors may include thermocouple wires deployed
alongside conductors designed to carry the electrical power. In
some embodiments, each system conductor may include a thermocouple
wire connected to a sensor in a junction box (e.g. junction box
711a), enabling the sensor to sense a rise in temperature at any
point along the conductor. In some embodiments, costs may be
reduced by deploying thermocouple wires only in short conductors
(e.g. output conductors 704aa, 704ab). In some embodiments, each
system conductor may include a Linear Heat Detection (LHD) coupled
to a controller in a junction box (e.g. junction box 711a). In some
embodiments, a rise in temperature at any point along the conductor
may cause the LHD wires to come into contact with one another,
triggering an electrical pulse that may be detected by a controller
configured to take action in response to receiving a pulse. In some
embodiments, costs may be reduced by deploying LHD wires only in
short conductors (e.g. output conductors 704aa, 704ab).
Reference is now made to FIG. 8A, which illustrates an integrated
electrical cable according to illustrative embodiments. Integrated
cable 800 may comprise conductor(s) 801 and heat detector 802.
Conductor(s) 801 may be made of copper, aluminum or other
appropriate conducting materials. In the illustrative embodiment of
FIG. 8A, conductor(s) 801 is illustrated having a single conductor.
In some embodiments, conductor(s) 801 may comprise several separate
conductors (e.g. 2, 3, 4, 5, 10, 20 or even 40 conductors), each
made of an appropriate conducting material. Heat detector 802 may
comprise wires 803 and 804. In some embodiments, wires 803 and 804
may be wound together to form a thermocouple pair configured to
measure temperature at a contact point. For example, the ends of
wires 803 and 804 may be coupled at a connection point in a PV
string, with a temperature sensor located in a power device (e.g.
temperature sensor 401 of power device 400) or a PV junction box
(e.g. junction box 711a) measuring the temperature at the contact
point via the thermocouple pair. If a temperature above a certain
threshold is measured, a controller and/or communication device
coupled to the sensor may take action (e.g. reporting a potentially
dangerous situation or disconnecting a circuit) in accordance with
embodiments disclosed herein.
Still referring to FIG. 8A, in some embodiments, heat detector 802
may be a Linear Heat Detector (LHD). Wires 803 and 804 may be
insulated, with the insulation designed to melt at a certain
temperature, creating an electrical contact between wires 803 and
804. For example, the insulation between wires 803 and 804 may be
designed to melt at a threshold temperature set with regard to
criteria described herein. Common LHD devices feature insulation
designed to melt at about 90.degree. C., 105.degree. C.,
135.degree. C. and 180.degree. C. In case of overheating at any
point in integrated cable 800, a local temperature may rise above
the threshold temperature, bringing wires 803 and 804 into
electrical contact which may create a short-circuit. Wires 803 and
804 may be coupled to a power device (e.g. temperature sensor 401
of power device 400) or a PV junction box (e.g. junction box 711a)
comprising circuitry designed to detect a short-circuit, and upon
detection, a controller and/or communication device coupled may
take action (e.g. reporting a potentially dangerous situation or
disconnecting a circuit) in accordance with embodiments disclosed
herein.
In some illustrative embodiments, wires 803 and 804 may be enclosed
in insulation 806, creating additional separation and isolation
from conductor(s) 801. In some embodiments, additional insulation
might not be necessary. Integrated cable 800 may include casing
805, which encloses conductor(s) 801 and heat detector 802 for fast
and easy deployment.
In some embodiments, heat detector 802 may comprise a thermistor or
resistance thermometer coupled in series to a single wire, with the
wire resistance measured periodically to detect a change in
resistance which may be indicative of overheating. The wire
resistance may be measured in various ways, such as applying a
voltage between the wire ends and measuring current.
Integrated cables similar to or the same as integrated cable 800
may be used in various systems. In some embodiments, PV panels or
other power sources may comprise one or more integrated cable(s)
providing electrical connection along with heat-detecting
capabilities. For example, a PV panel (e.g. PV panel 610) may
include an output conductor (e.g. output conductor 604b) which may
be a "regular" conductor, and one output conductor (e.g. output
conductor 604a) comprising an integrated cable such as or similar
to integrated cable 800. In some embodiments, PV power-devices
(e.g. power device 400) may comprise one or more integrated cables.
For example, a PV power device (e.g. power device 400) may feature
one output conductor (e.g. output conductor 404b) which may be a
"regular" conductor, and one output conductor (e.g. output
conductor 404a) comprising an integrated cable similar to or the
same as integrated cable 800. In some embodiments, a PV power
device may have one or more input conductors (e.g. input conductors
403) comprise an integrated cable. In some embodiments, integrated
cables may be deployed in homes, factories, shopping malls or in
any other electrical system where heat-detecting capabilities may
enhance electrical safety. Integrated cables may be deployed in
particularly sensitive parts of electrical systems, or more broadly
across entire systems.
Reference is now made to FIG. 8B, which illustrates integrated
heat-detecting electrical connectors according to one or more
illustrative aspects of the disclosure. Integrated connector 811
may comprise outer section 815, conductor pin 812 and
temperature-device pins 813 and 814. In some embodiments,
integrated cable 810 may be coupled to integrated connector 811.
Integrated cable 810 may be similar to or the same as integrated
cable 800 of FIG. 8A, with a conductor similar to or the same as
conductor(s) 801 coupled to conductor pin 812, and wires similar to
or the same as wires 803 and 804 coupled to temperature-device pins
813 and 814. In some embodiments, a connector similar to or the
same as integrated connector 811 may be part of an electrical
device, such as a PV power device (e.g. a DC/DC converter or a
DC/AC inverter), with conductor pin 812 carrying input current into
or out of the electrical device, and temperature-device pins 813
and 814 coupled to an appropriate control device.
Still referring to FIG. 8B, integrated connector 821 may comprise
outer section 825, conductor cavity 822 and temperature-device
cavities 823 and 824. In some embodiments, integrated cable 820 may
be coupled to integrated connector 821. Integrated cable 820 may be
similar to or the same as integrated cable 800 of FIG. 8A, with a
conductor similar to or the same as conductor(s) 801 coupled to
conductor cavity 822, and wires similar to or the same as wires 803
and 804 coupled to temperature-device cavities 823 and 824. In some
embodiments, a connector similar to or the same as integrated
connector 821 may be part of an electrical device, such as a PV
power device (e.g. a DC/DC converter or a DC/AC inverter), with
conductor cavity 822 carrying input current into or out of the
electrical device, and temperature-device cavities 823 and 824
coupled to an appropriate control device.
Integrated connectors 811 and 821 may be designed to fit together
for connecting to each other. Conductor pin 812 may be designed to
fit into conductor cavity 822, and temperature-device pins 813 and
814 may be designed to fit into temperature-device cavities 823 and
824. When integrated connectors similar to or the same as
integrated connectors 811 and 821 are connected to one another,
their respective conducting and temperature detecting elements may
be coupled to one another, for serial stringing of the conducting
and temperature detecting elements.
Referring back to FIG. 7, in some embodiments, connection points
CPa and CPb may comprise integrated connectors similar to or the
same as integrated connectors 811 and 821. Conductor 720 and/or
conductors 704aa, 704ba, 704ab, and 704bb may be similar to or the
same as integrated cable 800. In some embodiments, a (not
explicitly depicted in FIG. 7) system control device may be part of
an electrical device (e.g. a DC/DC converter, a DC/AC inverter,
and/or a photovoltaic combiner box used to couple multiple
photovoltaic strings in parallel) coupled between the
higher-voltage and lower-voltage power lines. Connecting the
integrated cables (e.g. conductors 720, 704aa, 704ba, 704ab, and
704bb) using integrated connectors may couple thermal devices (e.g.
thermocouple, LHD) may enable the system control device to detect
overheating at any point in the portion of a PV string depicted in
FIG. 7 without requiring deployment of a controller in multiple
locations.
Reference is now made to FIG. 9, which shows a flow diagram of a
method for detecting overheating in an electrical conductor
according to one or more illustrative aspects of the disclosure. At
step 900, a heat-sensing device is configured. The heat
sensing-device may be a thermocouple, LHD or similar heat-detection
device. Configuring the heat-sensing device may include one or more
design steps. For example, if the heat-detection device is an LHD,
configuring the device may include selecting insulation which melts
at an appropriate temperature. If the heat-detection device is
thermocouple device, configuring the device may include coupling
the device to a controller and setting a threshold temperature
which the controller may interpret as a potentially unsafe
temperature. At step 901, the heat-sensing device may be deployed
along with a conductor, in an integrated cable similar to or the
same as integrated cable 800. Deploying the device may comprise
physically connecting an integrated cable to other system devices,
as part of construction of an electrical system such as a PV
installation. Steps 902-904 may be similar to or the same as steps
102-104 of FIG. 1.
In some embodiments, it may be desirable to log temperature
measurements during "normal" system operation, both to provide
real-time operating information and to predict future system
events. For example, referring back to FIG. 3, circuitry 302 may
comprise a sensor 301 coupled over common bus 320 to memory device
309, communication device 303 and control device 305. The
measurements measured by sensor 301 may be stored on memory device
309, processed by control device 305 and/or communicated to
external memory or control devices via communication device 303.
The measurements taken by sensor 301 and/or sensors/sensor
interfaces 304 may be analyzed by one or more control/processing
devices for statistical patterns which may enable early detection
or prediction of potentially dangerous situations. Measurements
taken by many sensors deployed in many devices may generate a large
database of measurements. In some cases, measurements obtained from
a system which later experienced an unsafe condition may be
analyzed to detect trends which may be exhibited in similar systems
and may be indicative of an upcoming unsafe condition.
A myriad of predictive modeling and/or detection techniques may be
used to detect or predict unsafe conditions resulting from rising
or high conductor temperature. A partial list includes Bayesian
analysis, Machine Learning, Artificial Neural Networks (ANN),
Regression Analysis and Maximum a-posteriori (MAP) testing. For
example, in some embodiments, a linear regression may be used to
model the relationship between temperature at a conductor location
and other measurable system variables such as temperatures measured
at other system locations, voltage and current levels, current
harmonic content, solar irradiance and/or ambient humidity levels.
In some embodiments, an ANN may be trained to emulate a nonlinear
function and identify an upcoming instance of conductor overheating
by being trained using historical system data measured prior to
system safety events (e.g. overheating, fires, etc.).
As an illustrative, non-limiting example, historical data may
suggest that if a temperature measured by a temperature sensor
deployed 20 [cm] or less from a connection point is above
100.degree. for 10 [sec] or longer, and temperature is rising at a
rate of 1.degree. C./sec or higher and the current flowing through
the connection point is 10 [A] or higher, there is a significant
probability of the connection point overheating and a fire
starting. The actual thresholds may vary from system to system, and
those given above are illustrative examples.
Reference is now made to FIG. 10, which shows a flowchart according
to an aspect of illustrative embodiments. At step 110, data may be
collected from sensors, and "system events" may be logged. Step 110
may take place over a period of time such as a day, month, year or
several years. In some embodiments, step 110 may comprise
purchasing data from a database. Sensor data may include (but is
not limited to) measurements measured by voltage sensors, current
sensors, irradiance sensors, temperature sensors, humidity sensors,
and/or wind sensors. System events may include periods of normal,
safe operating conditions, and may also include (but are not
limited to) unsafe conditions such as arcing, overheating, fires,
system failure and/or short-circuit conditions. At step 111, the
data may be analyzed for patterns, using pattern recognition
methods designed to correlate groups of data measurements with
certain system events. Pattern recognition methods may include
supervised and unsupervised learning methods, and may include
various families of statistical and/or machine learning
techniques.
At step 112, the method begins monitoring system sensor
measurements. Measurements may be interpreted with regard to the
patterns detected at step 111. In some embodiments, the method may
proceed to step 113 each time a new sample is received, and in some
embodiments may proceed to step 113 at regular time intervals, or
after a series of samples is received. In some embodiments,
measurements obtained at step 112 may be added to the system
database, and the method may periodically return to steps 110-111,
adding recent samples to the collection of sensor data and
iteratively analyzing the collection of sensor data for recognizing
patterns.
At step 113, the method may evaluate the system state based on
previous measurements and a model developed for characterizing the
system. For example, the method may determine that a temperature
measurement of 100.degree. C. measured by a temperature sensor
(e.g. temperature sensor 401 or FIG. 4) indicates that the system
may be in a potentially unsafe condition. As another example
related to the illustrative embodiment illustrated in FIG. 4, the
method may determine that a temperature measurement of 90.degree.
C. by temperature sensor 401, in combination with a previous
temperature measurement of 85.degree. C. by sensor and a current
measurement of 10 [A] flowing through connector 408a (measured by,
for example, a current sensor comprising circuitry 402) may
indicate a potentially unsafe connection between connector 408a and
a corresponding connector.
If, at step 113, the system is determined to be operating safely,
the method may return to step 112 for continued monitoring of
sensor measurements. If a potentially unsafe condition is detected
at step 113, the method may proceed to step 114. At step 114, a
"potentially unsafe condition" protocol may be followed. In some
embodiments, the "potentially unsafe condition" protocol may
comprise a controller automatically disconnecting a portion of the
system from an electrical current. In some embodiments, the
controller may be coupled via a communication device to a wired
and/or wireless network(s)/Internet/Intranet, and/or any number of
end user device(s) such as a computer, smart phone, tablet and/or
other devices such as servers which may be located at a network
operations center and/or monitoring center. These devices may be
utilized to generate a warning of a dangerous condition, determine
when a dangerous condition is probable, detect the type of
dangerous condition and/or take action to degrade or turn off
certain portions a system. These warnings can be audio and/or
visual. They may, for example, be a beep, tone, siren, LED, and/or
high lumen LED.
The method illustrated in FIG. 10 may be carried out by one or more
control devices, either local or remote, with data-sharing and
communication taking place between various control devices.
Reference is now made to FIG. 11, which illustrates a system
control architecture according to an illustrative embodiment. Local
electrical system 120 may be coupled to sensors/sensor interfaces
121, controller(s) 122, communication device 123 and local memory
device 124. Interaction between the various local system devices
may be similar to described above with regard to previously
disclosed embodiments. Server 126, database 127 and communication
device 128 may be remotely located, e.g. at a management,
monitoring or command and control center. Communication devices 128
and 123 may be configured to communicate using wired or wireless
communication methods, such as cellular communication, or using
Power Line Communications. In some embodiments, the steps of the
method of FIG. 10 are carried out solely by local controller(s)
122, and in some embodiments, the steps are carried out by both
local controller(s) 122 and remote devices. For example, in some
embodiments, steps 110 may be carried out by purchasing data and
storing the data on database 127, step 111 may be carried out by
server 126, step 112 may be carried out by local sensors/sensor
interfaces 121 and controller(s) 122, step 113 may be carried out
by server 126, and step 114 may be carried out by controller(s)
122. In some embodiments, step 110 may be carried out by
sensors/sensor interfaces 121 taking measurements over time, and
transferring the data to database 127 via communication devices 128
and 123. In some embodiments, at step 114, communication device 128
may send a warning to user interface(s) 130, reporting a
potentially unsafe condition. In some embodiments, the entire
method (steps 110-114) may be carried out by local devices.
In the illustrative embodiments disclosed herein, photovoltaic
panels are used to exemplify energy sources which may make use of
the novel features disclosed. In some embodiments, the energy
sources may include solar shingles, batteries, wind or
hydroelectric turbines, fuel cells or other energy sources in
addition to or instead of photovoltaic panels. The temperature
detection methods, prediction techniques and other techniques
disclosed herein may be applied to alternative energy sources such
as those listed above, and the nearly exclusive mentioning of
photovoltaic generators as energy sources is not intended to be
limiting in this respect.
It is noted that various connections are set forth between elements
herein. These connections are described in general and, unless
specified otherwise, may be direct or indirect; this specification
is not intended to be limiting in this respect. Further, elements
of one embodiment may be combined with elements from other
embodiments in appropriate combinations or subcombinations. For
example, integrated cable 800 of FIG. 8A may be used as an output
conductor 404a of power device 400 or as output conductor 604a of
PV panel 610. As another example, the architecture illustrated in
FIG. 11 and described with regard to the method of FIG. 10 may also
be used to implement all or part of the method of FIG. 1.
Reference is now made to FIG. 12, which illustrates an integrated
thermal fuse 1020 according to aspects of illustrative embodiments.
Integrated thermal fuse 1020 may be disposed between walls 1021 and
1022, and may comprise conductor 1023, conductor 1024, pellet 1025
and spring 1026. During normal operating conditions, conductors
1023 and 1024 may be in electrical contact for carrying current in
a portion of a photovoltaic installation. Spring 1026 may be
compressed between wall 1022 and conductor 1024, and may apply
mechanical force to conductor 1024, in the direction indicated by
arrow 1027. Pellet 1025 may be disposed between conductor 1024 and
wall 1021, preventing or limiting movement of conductor 1024. Walls
1021 and 1022 may be portions of an electrical connector, for
example, two sides of connector 1008, which may be the same as or
similar to connectors 408a or 408b of FIG. 4. Connector 1008 may be
a photovoltaic module connector, for example, a photovoltaic
generator connector or a photovoltaic power device connector. In
some embodiments, walls 1021 and 1022 may be sides of an electrical
conductor such as conductor 1004, which may be the same as or
similar to output conductors 404a and 404b of FIG. 4. Pellet 1025
may be conductive or nonconductive, and may be made of various
materials or compound material including elements such copper, tin,
silver, beryllium, or ferrite. Pellet 1025 may be selected to have
a melting temperature in a range appropriate for disconnecting a
circuit according to the safety requirements of the installation
the fuse is disposed in. For example, in photovoltaic installations
where it is desirable to disconnect a circuit in response to a
temperature of 200.degree. C. at a connection point, a pellet 1025
which melts or is deformed at approximately 200.degree. C., or in a
range around, slightly above or slightly below 200.degree. C., may
be used. As discussed with regard to FIG. 1, a different threshold
may be selected depending on the flammability of materials near a
connection point where thermal fuse 1020 may be deployed. Spring
1026 may similarly be conductive or nonconductive.
If the temperature in or at integrated thermal fuse 1020 reaches a
temperature threshold selected to trigger a circuit disconnect,
pellet 1025 may melt, break or be disfigured. Upon pellet 1025
melting, breaking or being disfigured, spring 1026 may decompress
in the direction indicated by arrow 1027, forcing apart conductors
1023 and 1024, resulting in an open circuit connection.
It is to be understood that many different mechanical constructions
of a thermal fuse may be considered for use as part of an
integrated thermal fuse. For example, alternative constructions may
include a conductive pellet forming part of a current path, the
pellet melting at a predetermined threshold temperature and
disconnecting the current path. As another example, a conductive
spring may form part of a conduction path and may be compressed
against a pellet, whereby upon the melting or disfiguration of the
pellet, the spring decompresses and springs out of the conduction
path. As yet another example, spring 1026 may be extended rather
than compressed, with pellet 1025 disposed alongside spring 1026
and preventing compression of spring 1026, wherein under a high
temperature, pellet 1025 may break or become deformed, allowing
spring 1026 to compress and separate conductors 1023 and 1024. A
person skilled in the art may appreciate various alternative
constructions encompassed in embodiments described herein with
regard to integrating a thermal fuse in a connector or cable for
use in a renewable energy production installation.
Reference is now made to FIG. 13A, which illustrates a portion of a
photovoltaic string according to illustrative embodiments.
Photovoltaic generators 1010 may be coupled in series to form a
portion of a serial photovoltaic string. Each photovoltaic
generator 1010 may comprise junction box 1011, each junction box
1011 comprising a first output conductor terminated by male
connector 1008a and a second output conductor terminated by female
connector 1008b. Each male connector 1008a may be designed to be
connected to a female connector 1008b. In some embodiments, the
locations of male connector 1008a and female connector 1008b on a
junction box 1011 may be reversed or modified without departing
from the scope of the present disclosure. Junction box 1011 may
comprise conductors for receiving electrical power from junction
box 1011 and outputting the electrical power via the first and
second output conductors. In some embodiments, junction box 1011
may comprise a power converter (e.g. a DC-to-DC converter, or a
DC-to-AC inverter such as a microinverter), the converter
configured to adjust the converter input voltage and/or current to
increase power drawn from junction box 1011. In some embodiments, a
power converter embedded in junction box 1011 may include a Maximum
Power Point Tracking (MPPT) circuit, configured to increase the
power produced by photovoltaic generator 1010. In some embodiments,
junction box 1011 may comprise circuitry and/or devices depicted
and described in FIG. 3, for example, sensor(s) 304, communication
device 303 and/or safety device(s) 307.
Male connector 1008a and/or female connector 1008b may comprise an
integrated thermal fuse similar to or the same as integrated
thermal fuse 1020. In some embodiments, a thermal fuse may be
integrated in a male connector, and in some embodiments, a thermal
fuse may be integrated in a female connector, providing an
integrated thermal fuse at each male-female connection point. In
case of an overtemperature condition (e.g. due to a faulty
connection between connectors) at a connection point, the
integrated thermal fuse may trip, disconnecting the photovoltaic
string and preventing a continuing rise in temperature at the
connection point.
Integrating thermal fuses (e.g. integrated thermal fuse 1020) into
photovoltaic connectors may increase safety in photovoltaic
installations. The number and frequency of fires caused by faulty
connectors or a faulty connection may be dramatically reduced by
utilizing photovoltaic panels (either with or without junction-box
embedded DC-DC or DC-AC converters), photovoltaic converters,
batteries and/or other system devices with built-in thermal safety
fuses to prevent temperatures from rising above a predetermined
threshold such as 200.degree. C.
Reference is now made to FIG. 13B, which illustrates a portion of a
photovoltaic string according to illustrative embodiments.
Photovoltaic generators 1310 and junction boxes 1311 may be similar
to or the same as photovoltaic generators 1010 and junction boxes
1011 of FIG. 13A. Photovoltaic power devices 1300 may be similar to
or the same as photovoltaic power device 400 of FIG. 4, and may be
retrofitted to photovoltaic generators 1010. In some embodiments,
photovoltaic power device 1300 may comprise two output conductors
1304a and 1304b, which may be about the same length. Each conductor
1304a may be terminated by a male connector 1308a and each
conductor 1304b may be terminated by a female connector 1308b. Each
male connector 1308a or each female connector 1308b may be similar
to or the same as male connector 1008a and female connector 1008b
of FIG. 13A. For example, each male connector 1308a or each female
connector 1308b may comprise an integrated thermal fuse designed to
respond to an overtemperature condition and disconnect two
photovoltaic devices 1300.
Reference is now made to FIG. 13C, which illustrates a portion of a
photovoltaic string according to illustrative embodiments.
Photovoltaic generators 1320 may be coupled in parallel to form a
portion of a parallel photovoltaic string. Each photovoltaic
generator 1320 may comprise junction box 1321, and may be connected
between a ground bus and a power bus. Photovoltaic generators 1320
and junction boxes 1321 of FIG. 13C may be the same as photovoltaic
generators 1010 and junction boxes 1011 of FIG. 13A. The ground bus
and power bus may comprise first splice connector 1012a and second
splice connector 1012b for providing an electrical connection to a
photovoltaic generator. For example, the power bus may provide a
plurality of second splice connectors 1012b, each second splice
connector 1012b designed to be connected to a photovoltaic
generator female connector (e.g. female connector 1008b of FIG.
13A). Similarly, for example, the ground bus may provide a
plurality of first splice connectors 1012a, each splice connector
1012a designed to be connected to a photovoltaic generator male
connector (e.g. male connector 1008a of FIG. 13A). In some
embodiments, a thermal fuse (e.g. integrated thermal fuse 1020) may
be integrated into first splice connector 1012a and/or second
splice connector 1012b, the thermal fuse designed to disconnect a
photovoltaic generator from the splice connector upon an increase
in temperature in our next to the thermal fuse, to prevent a faulty
connection from causing a fire or other dangerous situation.
Reference is now made to FIG. 14, which illustrates a thermal fuse
connector 1400 according to illustrative embodiments. Thermal fuse
connector 1400 may comprise male connector 1408a, female connector
1408b and thermal fuse therebetween. Thermal fuse 1420 may comprise
conductors 1423 and 1424, and conductors 1423 and 1424 may provide
a conductive path between male connector 1408a and female connector
1408b. Spring 1426 may be compressed between wall 1421 and
conductor 1424, and may apply mechanical force to conductor 1424,
in the direction indicated by arrow 1427. Pellet 1425 may be
disposed between conductor 1424 and wall 1422 of thermal fuse 1420,
preventing movement of conductor 1424. Pellet 1425 may be
conductive or nonconductive, and may be made of various materials
or compound material including elements such copper, tin, silver,
beryllium, or ferrite. Pellet 1425 may be selected to have a
melting temperature appropriate for disconnecting a circuit
according to the safety requirements of the installation the fuse
is disposed in. For example, in photovoltaic installations where it
is desirable to disconnect a circuit in response to a temperature
of 200.degree. C. at a connection point, a pellet 1425 which melts
or is deformed at about 200.degree. C., or in a range around or
slightly below 200.degree. C., may be used. Spring 1426 may
similarly be conductive or nonconductive.
Male connector 1408a may be designed to be connected to a female
connector of a photovoltaic generator, such as female connector
1008b of FIG. 13A. Female connector 1408b may be designed to be
connected to a male connector of a photovoltaic generator, such as
male connector 1008a of FIG. 13A.
Referring back to FIG. 13A, some photovoltaic generators may have
been already constructed using photovoltaic generators which do not
include integrated thermal fuses. It may be desirable to add
thermal fuses to existing systems, and/or to add thermal fuses to
existing photovoltaic generators. Thermal fuse connector 1400 may
be connected to existing photovoltaic generators or systems by
connecting male connector 1408a to female connector 1008b of a
photovoltaic generator, and connecting female connector 1408b to a
male connector 1008a of a different photovoltaic generator.
Similarly, thermal fuse connector 1400 may be connected to
batteries, power converters, combiner boxes or other photovoltaic
devices featuring connectors similar to male connector 1008a and
female connector 1008b.
Reference is now made to FIG. 15, which shows a method for
operating a power converter according to illustrative embodiments.
Method 1500 may be carried out by a controller (e.g. a Digital
Signal Processer, Application-Specific Integrated Circuit, Field
Programmable Logic Array, Microcontroller, and the like) configured
to control a photovoltaic (PV) power device. At step 1501, the PV
power device receives photovoltaic power at the device inputs. In
some embodiments, the PV power device may receive photovoltaic
power directly from a photovoltaic generator. In some embodiments,
the PV power device may receive photovoltaic power from a group
string of photovoltaic generators connected in series or in
parallel, or may receive photovoltaic power combined in a combiner
box. At steps 1502 and 1503, the PV power device may convert the
power received at the input to power provided at the device output,
and provide the converted power to output terminals, respectively.
In some embodiments, the conversion may be from a direct current
(DC) voltage to a DC voltage of the same or a different magnitude.
In some embodiments, the conversion may be from direct current (DC)
to alternating current (AC). In some embodiments, conversion might
not take place, with input power being transferred as-is to the
output. At step 1504, the controller may check for an open circuit
condition at the device output. For example, a current sensor may
measure output current, with a low measurement indicating a
possible open circuit. An open circuit condition may be caused by a
thermal fuse (e.g. a thermal fuse embedded in first connector 1008a
or second 1008b of FIG. 13A, or a thermal fuse in a thermal fuse
connector 1400) being tripped by an overtemperature condition. If
no open-circuit condition is detected, the controller may return
from step 1504 back to step 1501 and continue receiving
photovoltaic power at the input.
If a potential open-circuit condition is detected (i.e. a thermal
fuse may have tripped), the controller may proceed from step 1504
to step 1505 and reduce the power received at the input. For
example, the controller may control switches to disconnect the
input from a source of photovoltaic power (resulting in zero input
current) or to short-circuit the input to the power device
(resulting in zero input voltage). In some embodiments, step 1505
may include reporting the open-circuit condition and safety
measures taken to a centralized control and/or data center.
It is noted that various connections are set forth between elements
herein. These connections are described in general and, unless
specified otherwise, may be direct or indirect; this specification
is not intended to be limiting in this respect. Further, elements
of one embodiment may be combined with elements from other
embodiments in appropriate combinations or subcombinations. For
example, integrated cable 800 of FIG. 8A may be used as an output
conductor 404a of power device 400 or as output conductor 604a of
PV panel 610. As another example, the architecture illustrated in
FIG. 11 and described with regard to the method of FIG. 10 may also
be used to implement all or part of the method of FIG. 1. As
another example, a power device may comprise one or more thermal
fuses integrated into one or more power device connectors (e.g., as
shown in FIG. 14), and may additionally comprise one or more
thermal sensors disposed in proximity to the connectors, as shown
in FIG. 2. The power device may be configured to provide a first
level of protection by reducing power drawn at the input connectors
in response to detecting an overheating condition, and the
integrated fuses may provide a second level of protection in case
the first level of protection does not provide a sufficient
response.
* * * * *